This invention relates to a composition for permanent waving of hair, which stimulates the rate of reaction and final curl efficiency while leaving the hair soft and lustrous.
Various compounds are used in permanent waving solutions because of their reactions with the keratin protein chains in the hair, which cleave the interprotein disulfide bonds. This softens the fibers of hair so that a wave can be formed. The wave can then be set by reversing the reactions with an oxidant such as hydrogen peroxide or sodium bromate. Suitable compounds include salts and esters of thioglycolic acid or thiolactic acid, beta-mercaptoethylamine, thioglycerol, cysteine, and sodium bisulfite. Thioglycolic acid salts are the most commonly used in commercial salon waving solutions, although some of the other materials find use in specific applications.
The principal salts and esters of thioglycolic acid used in commercial permanent wave solutions are ammonium thioglycolate (ATG), monoethanolamine thioglycolate (MEATG) and glyceryl monothioglycolate (GMTG). GMTG is an excellent nucleophile at a pH in the range of from 7 to 8 and has been the thioglycolate of choice for permanent wave solutions having a neutral pH. It would be desirable, however, to employ ATG in a neutral permanent wave solution since GMTG is an expensive chemical which must be packaged separately from other parts of the composition, which adds to its expense and imposes an extra difficulty in usage. Further, GMTG is purported to be an irritant or sensitizer which may limit its use for some individuals.
There are also times when it is desirable to have a "non-ammonia" wave solution where MEATG is the sole waving agent in the solution. These are difficult products due to their tendency to react very slowly with the hair and often give poor hair condition due to the difficulty in "reading" the progress of the wave by test curl procedures commonly practiced in the art. This often results in operator error and overprocessing of the permanent wave.
Further, it is desirable to accelerate curl formation and stabilization in an alkaline permanent wave solution so that the time required for processing can be reduced. It is desirable to have a solution that reproducibly processes hair in about five minutes instead of the twenty minutes typically required. The desirability of a five minute salon wave is apparent; the operators may be able to give twice as many permanent waves in a day as they can at present. A patron may be able to easily get a permanent wave during lunch hour. This has not previously been possible without using extremely strong solutions of thioglycolate and alkalinity which may severely compromise hair condition.
The isoelectric point of hair is about pH 3 to 5. It would be desirable to have a permanent wave solution having a pH in that range. Some sodium bisulfite permanent wave solutions have had a pH as low as about 6, but no truly acid solutions near the isoelectric point of hair are known. It would be desirable to have permanent wave solutions which have a pH approximately the same as the hair.